Changes in plant composition alter pollinator communities and pollination
Communities are subjected to community changes due to species extinction and colonization as a consequence of multiple natural phenomenons (perturbations, migration events, etc.). In the last decades, though, climate change is fostering shifts in species distribution, causing some native species to arrive into communities where they were absent.
Recently, researchers from CREAF, UAB, CSIC, Museu de Ciències Naturals de Granollers, and UAB, have conducted an experiment simulating the arrival of a native species into a natural community. Concretely, they introduced potted flowering Cistus albidus into scrublands (Montseny Natural Park) dominated by C. salviifolius, Lavandula stoechas (lavender), and Thymus vulgaris (thyme).
Changes provoked by the plant’s arrival were surprising. C. albidus acted as a magnet species, attracting bumblebees (Bombus terrestris) to the communities. Bumblebees are large bees with foraging distances of several kilometers. As C. albidus produces large amounts of pollen and nectar, bumblebees were rapidly attracted, tripling its abundance.
Bumblebees visited not only C. albidus but lavender, a plant for which they show a strong preference because it produces a lot of nectar and because bumblebees forage it efficiently. Bumblebees double their visits to lavender, becoming the most important pollinator of the plant, followed by the honeybees. This was detrimental for lavender, as bumblebees visit more flowers per individual plant, and in doing so they increase autopollination, with negative consequences on reproduction (less fruit and seed production). C. albidus arrival changed the ecological network, that is, the whole set of species and interactions.
On the one hand the network became more generalized, that is, pollinators visited more plants and plants were visited by more pollinators. This caused the arrival of more pollen of other species into the plant stigmas (something negative). But it also caused that some species like thyme were visited by a more diverse array of pollinators (something positive). The latter caused thyme’s reproductive success to increase as a consequence of C. albidus arrival.
This study simulates a process that is increasingly frequent under the climate change scenario, in which some plants are rapidly changing their distribution. These results show that ecological relationships between plants and pollinators are rapidly rearranged as a response to novel situations, and the observed changes in networks and reproductive success suggest that this variation can have consequences on the stability of systems as well as in evolutionary dynamics.
*This work has been carried out in the context of the PhD thesis of the main author.
Center for Ecological Research and Forestry Applications (CREAF).
Universitat Autònoma de Barcelona.
Hernández-Castellano, C., A. Rodrigo, J.M. Gómez, C. Stefanescu, J.A. Calleja, S. Reverté, i J. Bosch. 2020. A new native plant in the neighborhood: effects on plant-pollinator networks, pollination, and plant-reproductive success. Ecology 101(7): https://doi.org/10.1002/ecy.3046